I just acquired a 40 something gallon hex. To keep the weight down and considering the height gradient of the landscaping I want to do I've been considering PUR foam. It's called "Good Stuff" or something to that degree and the practive rock and root formations I've made so far all look great. What I want to know is what type of paint to use, how well it stands up against mold and any toxicity issues to avoid. I want to do a 1/2 land 1/2 water vivarium with a waterfall and live plants. Ive segregated spots for all the natural stuff and I'd like the water to run over the PUR Foam into the aquatic area. Any suggestions would be appreciated.